Oscillator



May 13, 1941. J. B. SHERMAN OSCILLATOR Filed Nov. 1, 1939 M mm H n MM m N E 0 m2 E T 0 W T PF. I S A F B. A/

v U E Patented May 13, 1941 OSCILLATOR Jesse B. Sherman, New York; NiYI assignor to Radio Corporation of America, alcorporation' of Delaware Application November 1, 1939, Serial No. 302,305-- 4 Claims.

This inventionrelates to oscillation generators and more particularly to an oscillation generator for use in a television transmitting or receiving system for producing the voltages that cause the horizontal or vertical deflection of a cathode raybeam inthe transmitting or receiving tube.

In cathode ray tubes where a beam of electrons is generated'and directed against a target electrode, some means is normally-provided for causing deflection of the'cathode-ray beam in horizontal and vertical directions in order that the cathode ray beam may be caused to scan or traverse the entire'target electrode. In oscillographic devices, the cathode ray beam is usually deflected horizontally at a predetermined rate while the beam is deflected vertically in accordance with the potential variation to'be observed. In all these instances it is generally desirable that the cathode ray beam be deflected uniformly with respect to time and accordingly, some appear as a true saw-tooth wave form. Furthermore, in such deflection circuits it is desirable that the cathode ray beam be returned to its initial point'of deflection as rapidly as possible, and that the time for such return occupy a period less than 10% of the entire deflection cycle.

Various deflection circuits have been devised for causing deflection of a cathode ray beam, but in most of these circuits an absolutely true saw-tooth wave form is not generated and in many instances additional circuit means must be added to correct for certain inherent nonlinearities in the voltage variation. Furthermore, in certain previously used deflection generators, synchronizing impulses of considerable amplitude must be used in order to definitely determine the frequency of oscillation of the generator, and in such instances it has many times become necessary to amplify the synchronizing impulses in order that the necessary amplitude for positive synchronization may be made available. reviously used deflection circuits have also been more or less complicated and have included a large number of circuit components, with the result that the circuits are difiicult'to maintain in'proper operatingcondition andloften become erratic in operation.

It isth'erefore one purpose of the present invention to provide a cathode ray deflection circuit which will directly produce voltage variations of the desired sawetooth' waveform in order electrode and an anode.

that the -ca'th'od'e ray beammay be deflected at aconstant' rate: and uniformly with respect to time:

Another purpose ofithe present invention is the provision of a new. andim'proved cathode" ray beam deflection circuit which is simple in operation and which includesa minimum of necessary circuit components;

Still another purpose. of I the: present invention resides-in the provision of a deflection generator which may be readily synchronized and which will fall into synchronous operation'with a series of driving impulses even. though the amplitude of the synchronizing impulses be .small.

Astill further purpose of the :present invention resides: in the provision of a cathode ray beam deflection generator which is-stable in operation and which may be utilizedifor causing deflection of the :cathode ray: beam-atdiflerent rates by choosing the proper circuit parameters.

Still other advantages and purposes of the presen't' invention will-become more apparent 'to those skilled in theart from a reading of the following specification and claims, particularly when considered with the drawing, wherein:

, Figure '1- represents the preferred form of the present invention, and

Figure 2 shows a series of curves of the voltage variations occurring at different points in the circuits Referring now to the drawing, and particularly to Figure 1', the circuit includes a pair of electronic paths or vacuum tubes l0 and I2. Each of these tubes includes acathode, a control The cathodes of each of the tubes are connected to-ground and their anodes ifiand 20 are each connected to a source of positive potential by-means of resistances 22 and 24 respectively. The control electrode [4 of tube I0" is connected'to ground by means of a grid'resistance 26', and this control electrode is also provided with a terminal 28'whereby the synchronizing impulses may be applied between the control electrode l4 and ground. The control electrode H! of tube I2 is also connected to ground by a grid resistance 38; the value of which is preferably made adjustable. The anode iii of tube l 0 is connected to the control electrode l8 of tube l2 by a coupling condenser 32, and the anode 20 of tube I2 is connected to the control electrode [4 of tube H] by a coupling condenser 34. A- charging condenser 36 is also provided and is connected between the anode 30 of the tube l2 and ground, so that when the tube I2 is non-conducting; the condenser 36 may be charged positively through the resistance 24, the rate of charge being determined by the size of the condenser 36 and the value of the resistance 24.

In the circuit arrangement as described above, the deflection generator appears to closely resemble a multivibrator, but in fact the operation of the system is materially different from a mul-tivibrator.

In describing the operation of the system it will be assumed that tube I is conducting, and that tube 12 is non-conducting. During this interval the condenser 33 will be charged linearly through the resistance 24 as described above, so that a gradually increasing positive potential is available at the output terminals 38 and 40. When a synchronizing impulse is applied to the terminal 28 in a negative direction, the tube It is biased to cut-off and accordingly, an abrupt rise in the potential of the anode l6 will result. The synchronizing impulses which are applied to the control electrode M are indicated by the curve A of Figure 2, and the corresponding abrupt rises in the potential of the anode it of tube 10 which occur in phase with the synchronizing impulses are indicated in the curve B of Figure 2. When the tube I0 is biased to cut-off, the sudden rise in potential of the anode It supplies an impulse to the control electrode [8 of tube 12 in a positive direction in order to permit the tube l2 to become conducting, since the impulses which are applied at this instant rise above the cut-off potential of the tube 12. (See curve C in Figure 2) The tube IE will then become conducting, and will substantially instantaneously discharge the condenser 36, causing a sudden drop in the potential which is available at the output terminals 38 and 40. The drop in the potential of the anode causes the appearance of a negative impulse at the control electrode M of tube l0, which assists the synchronizing irnpulses and positively assures that the tube l0 remains non-conducting during the discharge of condenser 36. When the condenser 36 is completely discharged, the voltage rises at the anode 20 of tube l2 and this corresponding rise removes the negative potential which was applied to the control electrode I4 of tube 10, resulting in the re-establishment of a current flow through tube 10 and a corresponding decrease in the potential of anode I6 of this tube. Simultaneous with this operation the discharge tube I2 is again rendered non-conductive because the control electrode is of this tube is driven negative, and as soon as tube 12 is biased beyond cut-ofl, the condenser 36 begins charging, thus completing the cycle of operation. The high negative potential of the control electrode l8 of tube i2 is gradually diminished through the adjustable resistance 30, so that it is near the cut-off potential of tube I2 at the time the next succeeding positive impulse is applied to the control electrode l8 through the condenser 32 from the anode iii of tube l0 as indicated by curve C.

This cycle of operation will be repeated and the deflection generator will operate in synchronism with the applied synchronizing impulse to produce the desired deflection voltage wave form.

Accordingly, at the output terminals 38 and 40 may be derived a voltage variation of saw-tooth wave form which is linear in form and which will cause a constant rate of deflection of the deflected cathode ray beam. This wave form is shown at curve D in Figure 2.

Although no values for the various condensers and resistors are shown in the drawings, the following values are found to be desirable for two predetermined rates of deflections. These two rates of deflections are given in view of the fact that they correspond to the vertical and horizontal deflection rates in an electronic television system.

For 60-cycle deflection, resistance 26 is 20,000 ohms; resistance 22, 200,000 ohms; resistance 30, l megohm; resistance 24, 500,000 ohms; condenser 34, 0.01 micro-farads; condenser 32, 0.01 micro-farads, and condenser 36, 0.5 microfarads.

For 13,230 cycles per second, resistance 26, 1,000 ohms; resistance. 22, 200,000 ohms; resistance 30, 500,000 ohms; resistance 24, 200,000 ohms; condenser 34, 0.0004 micro-farads; condenser 32, 0.0004 micro-farads, and condenser 36, 0.004 micro-farads. It is obvious that various other values for the condensers and resistors may be chosen in accordance with the desired frequency which is to be generated.

The resistance 30 is made adjustable in order that a certain range of control may be had over the frequency of operation of the system, and the value of this resistance should be so chosen as to preclude conductivity of tube [2 prior to the occurrence of the synchronizing impulse and. the accompanying positive impulse from the anode IE of tube II).

It is possible that the system may be made to operate without the introduction of a synchronizing impulse, and such use of the system may be desirable in cathode ray Oscilloscopes. In this case adjustment of the resistance 30 will afford a certain control within a predetermined operating range over the frequency generated by the system.

From the above it may be seen that a new and improved cathode ray beam deflection circuit has been devised which is simple in operation and which will produce directly the desired wave form necessary to cause linear deflection of a cathode ray beam.

In actual practice it is customary to combine the two tubes l0 and I2 into a single envelope, since double triodes are available on the market and an example of such a tube is the conventional type 6N1.

One particular advantage of the present invention, especially when used in television receivers, resides in the fact that the system will operate upon the atplication of negative synchronizing impulses, and since negative impulses may be used, they may be obtained directly from the output of the synchronizing signal separator tube (clipper) in the television receiver. With most previously used oscillators, it is generally necessary to cause synchronization of the oscillator by applying thereto positive synchronizing impulse, which of course requires the addition of a phase inverter tube in order that the synchronizing impulse as derived from the separator tube in the receiver may be converted from negative impulses to positive impulses. With this system it may be seen, therefore, that the deflection generator may be coupled directly to the synchronizing separator tube of the receiver, and furthermore, in View of the sensitivity of the circuit described herein, the amplitude of these impulses as so derived is entirely suificient to cause synchronous operation of the deflection generator.

Various alterations and modifications may be made in the present invention without departing from the spirit and scope thereof, and it is desired that any and all such modifications be considered within the purview of the present invention, except as limited by the hereinafter appended claims.

I claim:

1. An oscillator for producing voltage variations of saw-tooth Wave form comprising a first and a second electron tube each having a cathode, a control electrode and an anode, means for connecting each of the cathodes to ground, means including separate resistances for maintaining each of the anodes positive with respect to its associated cathode, separate resistances for connecting each of the control electrodes to ground, means including a condenser for connecting the anode of the first electron tube to the control electrode of the second electron tube, means including another condenser for connecting the anode of the second electron tube to the control electrode of the first electron tube, a charging condenser connected between the anode of the second electron tube and ground, an output circuit connected to the anode of said second electron tube, and means for applying negative synchronizing impulses to the control electrode of said first electron tube whereby the tubes may be rendered alternately conducting and whereby a voltage variation of substantially linear saw-tooth wave form may be caused to appear across said charging condenser.

2. An oscillator for producing voltage variations of saw-tooth wave form comprising a first and a second electron tube each having a cathode, a control electrode and an anode, means for connecting each of the cathodes to a common conductor, means including separate resistances for maintaining each of the anodes positive with respect to the common conductor, a resistance for connecting the control electrode of said first tube to the common conductor, adjustable resistance means for connecting the control electrode of said second tube to the common conductor, means including individual condensers for connecting the anode of each electron tube to the control electrode of the other electron tube, an electron storage device connected between the anode of the second electron tube and the common conductor, and means for applying negative driving impulses to the control electrode of said first electron tube whereby the tubes may be rendered alternately conducting and whereby a voltage variation of substantially linear saw-tooth wave form may be caused to appear across said electron storage device.

3. An oscillating system for producing voltage variations of saw-tooth wave form comprising a pair of electronic paths, each path including a cathode, a control electrode and an anode, means for connecting the cathodes to a common conductor, means including individual resistances for connecting each of the control electrodes to the common conductor, means including separate resistances for maintaining each of the anodes positive with respect to its associated cathode, means including individual condensers for connecting the anode of each electronic path to the control electrode of the other electronic path, an electron storage device connected between one of the anode of one of the electron paths and the common conductor, means for applying negative potential impulses to the control electrode of the other of the electronic paths whereby voltage variations of substantially linear saw-tooth wave form maybe produced across the electron storage device, and an output circuit connected across said device.

4. An oscillator for producing substantially linear voltage variations of saw-tooth wave form comprising a pair of electron paths, each path including a cathode, a control electrode and an anode, means for connecting the cathodes together, means including individual resistances for connecting each of the control electrodes to the cathodes, separate resistances for maintaining each of the anodes positive with respect to the cathodes, means including individual condensers for connecting the anode of each electron path to the control electrode of the other electron path, a storage condenser connected between the anode of one of the electron paths and the cathodes, and means for applying negative potential driving impulses to the control electrode of the other electron path whereby voltage variations of substantially linear saw-tooth wave form may be produced across the storage condenser.

JESSE B. SHERMAN. 

